


A New Toy for the Toybox

by PineByPine (Tyrannosaurus_Sex)



Series: Three Saplings (A Triplets AU Series) [6]
Category: Gravity Falls
Genre: Aged-Up Character(s), Gender or Sex Swap, Multi, Threesome - F/F/M, Threesome - F/M/M, Triplets
Language: English
Status: Completed
Published: 2019-07-05
Updated: 2019-07-05
Packaged: 2020-06-13 03:38:28
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,035
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/19592620
Author URL: https://archiveofourown.org/users/Tyrannosaurus_Sex/pseuds/PineByPine
Summary: Same shit, different day. Another magic amulet, but it's gender changey powers make Dipper insecure.





	A New Toy for the Toybox

Dipper brushed the dust off his hands and looked around the cave, just to be sure that the ghosts really were gone. “I don’t want to sound cocky, but I think we’re getting better at this.”

Mabel pumped her fist in the air. “Booyah! Don’t nobody mess with the Mystery Triplets!”

Ty knelt by the pile of dust where the spectre had disintegrated and brushed some away with her hand. “I feel a little bad for them; we don’t even know why there were trying to possess people.” Her fingers wrapped around a glint of silver and she lifted it to reveal a pendant on a black silk cord. “What the heck is this?” She held it up for her siblings to view.

Mabel reached out and cupped the pendant, running her thumb over the surface. “It’s pretty.”

“Girls, that’s probably cursed.” Dipper gave them a worried look. “Mysterious amulet, left behind by a departing spirit, totally prime curse material.”

The eldest triplet made a raspberry noise. “Even if it is, who better to deal with a cursed amulet than us? We’re badasses.” She gingerly extracted the chord from Ty’s grip and held the item up. The pendant spun in the air.

“Huh,” Ty peered at it, “why would it have a male symbol on one side and a female on the other?”

“Only one way to find out!” Mabel pulled the loop of the cord open and stuck her head through. 

Both Ty and Dipper started to yell in surprise and reach out for her, but were startled into silence when nothing happened. Mabel stuck out her chest and grinned. “See? It looks good on me.”

Dipper’s brow furrowed. “Could be a trick, maybe it took over her mind or something. Quick, what’s something that only the real Mabel would know?”

Ty considered this for a second, then glanced cautiously at her brother before turning to Mabel and whispering something in her ear. Mabel’s face screwed up in disgust but she gave the answer back into Ty’s ear. The middle triplet then nodded to Dipper. “Nope, it’s the real Mabel.”

“Wait, what did you ask her?”

Both girls crossed their arms at him and glowered. “You really don’t want to know the answer to that question.” Ty added.

Dipper conceded and they began the trek back to the Mystery Shack, Mabel playing with the pendant the whole way. After about twenty minutes of walking, Ty caught up with Dipper and snatched his hand in hers. Dipper glanced around nervously, instinctively checking to see if there was anyone in sight. They were, of course, completely alone.

Ty smiled and stopped walking. As Dipper continued, she tugged his arm, causing him to spin around and she drew herself up to him, her free hand going to cup the side of his face. She had to rise on her tip toes just a little so their lips could come close. On her mouth, she could feel his breath suddenly go quick and shallow. Dipper’s hands went to her hips. His head started to tilt as they both leaned in.

Ty’s face became a scene of shock as she looked over Dipper’s shoulder. “Who the hell is that?!”

Dipper spun on his feet, hands suddenly clenched and arms ramrod straight down the sides of his body, trying to do his best impression of someone who wasn’t just about to do anything, no matter what anyone saw. He looked for the unseen witness but his eyes found only empty woodlands.

Then he heard his sister laughing. “Oh man, you are so easy, Dip.” She managed to say between gales of laughter. “I don’t think that will ever get old.”

He fumed for a moment then his face resolved into a wry grin. He raised his hands, winding the fingers menacingly in the air. “Oh you want to laugh, do you?”

Ty tried to defend herself, but Dipper’s tickling hands were quick and well practiced. She turned to try and flee, but he caught her up in his arms and worked his hands down to her sides, tickling furiously. Her giggling was unceasing and after a moment the actual sound of laughter stopped altogether, her breath gone.

“Oh sweet,” Mabel said from a few yards behind them. “So that’s what it does.” 

Dipper gave Ty a break and helped her regain her balance on the leaf littered ground. They both turned to their sister to see her, arms wide, giving them a huge proud grin. Dipper couldn’t immediately recognize what had happened, but something about Mabel looked off, like a slight funhouse mirror effect that he couldn’t put his finger on.

Ty’s mouth fell slack and her eyes wide. She finally managed to stammer. “What the… Where are the girls?” 

“Ruth Boobie Ginsberg and the Funtime Gang have left the building.” She puffed her chest out even more. Mabel hadn’t changed much over all, same build, same height, same hair, but there had been a slight shift of her features and some of her curvy places were no longer so curved. For example, she was certainly flat as a pancake now. Dipper watched as his sister reached down and lifted the hem of her skirt. “But on that note: Dipper, Ty, meet Mr. Pickle.”

Dipper felt like a sledgehammer had hit him in the gut. Whatever the amulet had done had not been a wholly subtractive process. Dipper was no longer, technically, looking at his sister.

Ty rushed past him, over to Mabel and gave her a toe to head once over while Dipper was still reeling. She pointed down at Mabel’s crotch. “May I?”

Mabel nodded and Ty reached down, hooked a finger in the hem of Mabel’s kitty adorned panties and pulled them out away from the skin. She peered in and immediately clapped her hand over her mouth in astonishment. She looked back up to Mabel’s face, then suddenly flashed with worry. “This isn’t permanent, is it?”

Mabel responded by reaching up with one hand and flipping the little amulet, currently showing the circle and arrow, around to show the circle and cross. There was a sort of wobbly distortion in the air and then Mabel was back to normal.

Dipper finally managed to break through the shock. “What the hell were two ghosts doing with something like that?”

“Ohhhh,” Ty smacked her forehead with one hand, “it was one ghost switching around, not two ghosts. That explains a lot.”

“No it doesn’t!” Dipper was almost yelling. His sister’s turned to consider him carefully and saw that his whole body was tensioned tighter than a snare drum. His face had already reached a shade of deep red and he was pointedly avoiding looking at them.

“Is everything alright, Big D?” Mabel asked.

“It’s fine!” The muscles of his jaw work furiously as he ground his teeth.

“Ok,” Ty tried to sound reassuring, “well, since everything is fine. We’re just going to sit down for a minute and catch our breath.” She turned and found a handy rock to rest on. As she got Mabel to sit as well, she discreetly kept her attention on Dipper.

After a minute or so, some of the anxiety seemed to have bled off him; he stepped over and plopped on the ground in front of his sisters, leaning his back against their knees. Mabel reached a hand out and ran her fingers through the hair on the back of her brother’s head.

Another few minutes of silence passed before Mabel leaned over and gave him a peck on the temple. “You wanna talk about it, broseph?” 

He took a deep breath. “OK, first off, you scared me. Fucking around with magical shit is dangerous; you both should know that better than anybody else.”

“Noted.” Ty slid from the stone to the ground next to him and put her arm around his shoulders.

“Second,” he continued, “it’s not nice to fuck with a guy like that.”

Ty glanced back over her shoulder to exchange a look with Mabel, who shrugged. She turned to Dipper. “What do you mean, Dip?”

“I mean, you two doing that look down the panties thing right in front of me.” He hunched his shoulders as if trying to hide. “Trying to turn me on while Mabel’s a dude.”

The sounds of the wind in the treetops was the only thing audible for a few seconds. Mabel gave her brother’s head an extra scratch. “Sorry, Dippin-sauce. We weren’t trying to do anything like that.”

There was another pause before Ty spoke. “Would you like us to?” 

She immediately felt his shoulder muscles stiffen. His reply was almost mumbled. “I’m not gay.” 

Ty felt her heart sink a little with realization. “Yea,” she proceeded carefully, “neither am I. Neither is Mabel, last I checked. Mabes dear, have you become gay anytime recently?”

Mabel tapped a finger to her chin and stared up at the trees for a moment as if seriously wracking her memory. Then she flopped down on the other side of Dipper. “Nope, still just a big ol’ pinesexual here.” She propped her head on his thigh.

Dipper snickered and some of the tension went out of air around them.

Ty’s eyebrows knitted together as she thought for a moment. “We never have talked about this. Even me and you, Mabel.”

“Talked about what?”

“Our sexualities. I know I’ve given it a lot of thought but I realized I have no idea what you two consider yourselves.”

Mabel shrugged hugely. “I dunno. Pinesexual sounds good to me.”

“You don’t find other people attractive? Really?”

Her sister avoided her gaze for a moment, then blushed. “OK, you promise not to be mad?”

Dipper gave her a quizzical look. “Why would we be mad?”

Mabel put her hands over her face. “Cause people get all jealous when their girlfriends admit they think other people are sexy. It doesn’t mean anything. Blargh! I just sometimes get these thoughts.”

Ty made a cross-my-heart movement with her free hand. “No punishment for the truth here. That’s our motto.”

Mabel peeped out between her fingers. “I thought our motto was ‘Triple scoop cones or nothing.’”

Dipper chimed in. “I’m still voting for ‘Nos elucidare tenebris’.”

Ty groaned. “Ok, motto discussion tabled until the next meeting. I’d still like to know whom Mabel finds sexy.”

“Buttercup and Westley.” She bit her lower lip and shrank a little as if expecting an explosion.

“Oh yea? Both?” Dipper cocked an eyebrow at her and she nodded.

“They’re both just so cute and they way they look at each other: sploosh!”

Ty nodded and made an acquiescent expression. “I see what you mean.”

“OK, what ‘bout you, Ty-dye?”

“I’d say I’m not gender discriminatory. If I was inclined to admit I was predisposed to one or the other, I probably lean a little toward men.” She shifted and her voice suddenly urged correction. “Not that that means I’m anything but equally attracted to you two. I’m just talking sort of statistically.”

Dipper put his own arm around her waist. “Yea, we get it.”

“Well, what about you, Dipster?”

He frowned. “I already said; I’m not gay.”

Ty rolled her eyes. “So we know what you’re not. What sort of people do you like?”

“I like girls.” He refused to look at either of them.

“Alright then.” Ty sprung to her feet and started to dust off her butt. “We should probably be getting back before Grunkle Stan starts to actually wonder where we’ve gone.” She reached down and helped Mabel to her feet.

Dipper rose slowly, as if cautious. “That’s it?”

Ty patted his cheek. “If that’s what you’d like.” She turned to her sister and grabbed her hand, starting back on the way toward home. “So, after dinner we’re digging out your copy of The Princess Bride and we’re gonna swoon all over it.”

Mabel giggled. “Yes! Swoon-city, here we come.”

* * *

The air in the attic was perfectly still and suffocatingly hot. All of the warmth from the whole shack rose into this small room and just hung there like a huge spider. Dipper wiped his forehead and stared at the dark ceiling for a while, unable to let his mind rest. Eventually, he felt compelled to rise and open the small window. Cool Oregon night air washed over his face and shoulders. He breathed in a huge lungful of it.

Dipper turned, leaned his butt against the window sill, and looked at his sisters curled up together in other bed. Ostensibly, one of the three of them was using the old air mattress every night, but that hadn’t happened all summer. He wished they’d had a properly big bed up here and could all pile in together, but trying to arrange for that sounded like the kind of thing that Dipper worried would arouse suspicion.

Slowly, he slid down the wall until he landed on the wood plank floor. He ran both hands through his shaggy hair and sighed.

_ What is up with me? _ He thought.  _ I haven’t felt this stressed since before me, Ty, and Mabel took things to the next level. _

Every time he closed his eyes, he was back in the woods again, watching as his sister looked coquettishly down at the contents of Mabel’s panties. Except in that moment, Mabel hadn’t really been Mabel. Had she? Mabel was the girliest girl Dipper could think of. She’d still been wearing a skirt and makeup, still had her long hair and feminine hips. If Dipper had been ten yards farther away or Mabel hadn’t lifted her damn skirt, he wouldn’t even had realized what was different. Did the actual equipment so freak him out that even the implication of another dick being near was enough to send him into panic mode?

And that infuriatingly knowing look on Ty’s face while they’d been talking about it after irked Dipper. Their middle triplet always thought she knew him better than he knew himself and it drove him crazy. He knew she had some notion about him, some fool idea that she was harboring away in that head of hers, smugly enjoying how right she thought she was about something he didn’t agree with. And then she’d refused to push him on it so he could actually argue back and convince her.

Dipper recognized that he’d gotten himself worked up by now and that sleep was probably farther off than it had been before. He pushed himself off the floor and headed downstairs to get something to drink. He returned, half a glass of milk later, to find the girls awake. Ty was sitting against the wall with Mabel’s head in her lap.

“Trouble sleeping, bromancer?”

He nodded and took another gulp of milk, set the glass on the table, and sat heavily on their bed. Mabel lifted her feet out of the way as he dropped then placing them on his knees. Dipper reached out in the pale light of their attic window and rubbed the soul of one, causing her toes to curl in her socks.

After a few minutes of quiet between them, Mabel rose from Ty’s lap, put a knee on either side of one of Dipper’s legs and leaned in to kiss him deeply. Her nails lightly dug into his shoulders as she gripped him hard, the passion of her lips on his growing in intensity. When they parted, both where breathing heavily. Dipper looked up into Mabel’s face and she smiled at him, brown eyes shining in the dark of the room.

Ty slid down the bed until she was next to Dipper and Mabel readjusted to straddle one leg of theirs each, her knees in the spaces between. Ty’s hand rose to run her fingertips lightly along the skin of Mabel’s arm and Dipper felt her other hand find his to intertwine their fingers.

Dipper’s eyes fell to glint of silver that fell nearly between Mabel’s breasts and he felt his heart almost stop. He actually felt compelled to check that the female symbol was showing, despite the obvious curvy nature of its surroundings. And then something, Dipper told himself it was the same feeling one gets when standing near a railing by a high fall, made him reach up and touch the silvery metal.

The three of them were as still as glass for a moment before Mabel spoke. “Go ahead, if you want.”

Dipper tried to swallow and found his throat was as dry as old parchment. He could hear the blood pounding in his ears. Ty squeezed his hand with hers. He felt so confused. Did he want this? If he did, then why?

With a small movement of his thumb, Dipper turned the little amulet over. 

“I can’t decide if this is weird or not,” he struggled to articulate, “being this intimate with a guy.”

Mabel put hands on hips and cocked a smile. “Ha!” She derided. “It takes more than a weiner to make Mabel Pines anything but a lady.” She leaned down and kissed him again, and it was just like kissing Mabel always had. It was, at least, until he felt her excitement growing stiff against his thigh.

Dipper felt Ty grasp the bottom hem of the oversized t-shirt Mabel wore a PJs and pull it up. He broke the kiss to allow the garment to pass over Mabel’s head and be cast aside. The oldest triplet knelt between their legs and stretched her arms languorously above her. He gazed up at her and put a hand against her stomach, pulled taut by her arching spine. His hand fell, gliding over the smooth skin of her hip until he could reach around and squeeze one cheek of her bottom.

Mabel finished her stretch and gazed down at them with half-lidded eyes, smiling. Then in a flash she had Ty’s own shirt off and tossed across the room. She sat back on their legs and licked her lips, then leaned forward a took her sister’s nipple into her mouth. As her body moved forward, Dipper caught a glimpse of the tip of her dick poking up out of the waistband of her panties.


End file.
